Seal and terminal for electric apparatus.



No. 830,249. PATENTED SEPT. 4, 1906.

H. N. POTTER. SEAL AND TERMINAL FOR ELECTRIG APPARATUS.

AIPLIOATIOH FILED JAHJI, 1904.

UNITED sragas PATENT OFFICE.

HENRY NOEL POTTER, OF NEW ROCHELLE, NEW YORK, ASSIGNOR TO COOPER HEWITT ELECTRIC COMPANY, OF NEW YORK, N. Y., A COR- PORATION OF NEW YORK.

Specification of Letters Patent.

Patented Sept. 4, 1906.

Application filed January 11. 1904. Serial No. 188,494-

To all whom, it may concern.-

Be it known that I, HENRY N OEL POTTER, a citizen of the United States, and a resident of New Rochelle, county of IVestchester, State of New York, have invented certain new and useful Improvements in Seals and Terminals for Electric Apparatus, of which the following is a specification.

It has heretofore been roposed to employ uartz as an inclosing chamber for various ectrical and other devices, wherein its chemical and optical properties render it more advantageous than glass. One difficulty in the use of such material for such purposes has been that no electric conductor has hitherto been found which will form therewith a tight seal or conductor for leading electric current through the walls of the chamber. The nearest approach to this has been with metallic iridium, which is refractory enough, but which has an expansion coellicient differing sufficiently from quartz to prevent the seal remaining tight when cooled to ordinary temperatures. A seal made of iridium requires in addition an application of shellac or similar material to render it tight, and consequently a vessel so made could not be heated in the region of the seal to temperatures sufliciently high to adapt it for many uses, especially for those which require a permanent high vacuum or a vapor existing at high temperatures, and for various other reasons such a seal has been found impracticable for permanent uses.

I have discovered that silicon in its socalled metallic state has all the properties which adapt it for use as a seal in quartz vessels and that with metallic silicon such seals can be made which are tight and by means of which current can be caused to pass through the wall of the vessel in practical quantities and which seals are not injured by being heated to a red heat or even higher. The expansion cocficient of metallic silicon seems to be approximately that of silica. It is further not oxidizable even at a white heat in the absence of such gases as carbon dioxid, for instance.

In practice I find an excellent way is to produce the metallic silicon in the form of a round rod or wire, which can be readily done by grinding on an emery-wheel and slipping the said rod within a tube of quartz, so that the quartz-tube projects beyond the rod of silicon. If then the quartz be heated externally opposite the silicon rod in an oxyhydrogen flame, the rod can be caused to melt, and it will then Wet and adhere to the silica and will not separate from the latter when cool ing. If it is further desired to expose the silicon, the silica may then be removed by grinding or any ether appropriate we and con tact made with the silicon either by Welding directly to platinum or by dipping inmercury or in any other appropriate manner. Should any slight oxidation occur on the inner surface of the silicon seal, preventing its making good electrical contact with the mercury or other conducting material within the vessel, the slight coating of oxid can be readily removed by dissolving in very dilute hydrofluoric acid. This acid will of course also attack the vessel of quartz; but the oxid film is so extremely thin as to be irridescent, and it is almost instantly removed, so that the injury to the quartz vessel is negligible.

In case it is desirous to produce the seal without the slightest danger of oxidation or a combination with any flame-gases which may enter the tube, Ifind it entirely practicable to pass a slow current of inert gas, such as hydrogen, through the vessel during the period when the seal is being formed. This insures that the silicon is surrounded with an inert gas 'u to the instant of wetting the silica and also t at the inner end of the silicon shall remain unchanged.

Metallic silicon is a good conductor of electricity of about the order of carbon, but has an advantage over carbon in that it is not porous, that it can be melted and cast into convenient preliminary shapes, that it does not oxidize in air even at white heat, and that it can be fused directly to platinum and other metals. In the case of metals likely to oxidize a flux, such as borax, may be used with success. It is advantageous, however, to select as a metal one having a small coefficient of expansion with change of temperature. I have found a good material to be nickel-steel containing approximately 36.4 per cent. of nickel, this material having the least known coefficient of expansion among metals and being known as the Guillaume alloy.

I may mention as one very important use of this invention the application of it to the latter is transparent to u operated-at temperatures which are not rmissible with glass of any kind, and'there ore metals other than mercury may be readily used as a source of conducting vapor. ther, the quartz is more inert to chemical attack than glass, andsuch metalsas antimony,

bismuth, and'lead in a melted or gaseous state do not attack quartz. There is alsoan advantage in the use of quartz for mercuryvapor devices in that the current density can be ushed far beyond what is possible in glass wit its attendant advantages. e

In the accom anying drawings. which.

illustrate, an app ication of the invention, Figure-1 shows a process of sealing the s1 hcon to the quartz, an Fig. 2 illustrates an application of. the invention to a Cooper Hewitt mercury-vapor lamp.

I Referring. to the drawings, 1 represents a quartz-tube. inserted loosely therein.

This-gas is passed through cury-vapor I quartz. 1

of the leading-in conductor 6 by a conductor 9; :An exterior conductor 10 is likewise faste'nedto the exterior surface of the leading-in conductor 6. These two conductors I'njay'be,

' of platinum, nickel-steel, or other suitable 5o material and'fused directly to the silicon.-' In In the case of a lamp Fur- herein.

f 1.. The combination with a quartz inclos- 2 represents a plug of silicon,

like manner the conductor 11 may be sealed to the leading-inconductor 7 and at 12 I other materials thanmercury may be employed in this chamber for 'aiiording a'conducting-path. V y I In another application filed by me on the 19thday of November, Serial No. 181,756, claims 1 are made upon method described I claim as my inventioning; chamber, of a leading-in conductor consisting of-silicon.v

q :2. The combination with a. inclosingchamber of quartz ofa gas-tight leading-in conduetorcom osed of metallic silicon.

U5 3.' The com ination with an inclosing chamber, of a gas or Va or electric conductor, and leading-inlcoii uctors formin termlnals therefor, conslstlng of metallic s1 icon.

" 4. 'The combination 'with an inclosing chamber! the main portion of the wells of which are of quartz, of leading-inconductors I consistin 3 represents a soureeof heatofany suit able character, such, for instance, asan oXyT- hydrogen flame. Y I I A source of inert gas, such as'hydrogen', is-

illustrated at 4. the tube 1, while sufficientheat is a ilied to melt the silicon and fuse-it to the s1l1ca.- It". should be stated, however, that the process I of passing-the inert'gas through the tube is. -not essential. l i q In Fig. 2, 5 representsth e' wall of a"merlamp composed of ,silica or 6 and 7 representle'ading-in cenuctors of silicon. 8. represents a solid electrode of any suitable character, which is here shown as being attached to-the inner surface of siliconand forming other por- -.t-l.Ol'.-'S.Df the, Walls of the chamber. a 1

5 A; as or-va or electric device, 00I1SlSl' 8O ingiof a uid-oon uctfor',,the vapor of the said fiuid,' an ,inclosing chamber of silica, and electrical connections-through the said containingvess'el contacting with said fluid or vapor, consistingof silicon.

6. Asanarticleof manufacture, an inclosint; chamber .for preserving oaeua composed partly "of silica and partly of silicon.

117. The cornbinationxwith a transparent: inclosing chamber. for gas or vapor e devices, of a leading in conductor oom' osed of silicon extending through the w ll and formingan.inner terminal. 1 Signed atNewYork, in the county of New York and State of New York, this31 'd of December, A.:D. 1903.

Y HENR N ELI POTTER...

ectric' 9o 

